Actually Yee, I'm thinking of Chlorophyll/Swift Swim Pokémon that carry their weather of choice. I've run Sunny Day Lilligant in the past and am currently using a Rain Dance Kingdra. In addition to having a super-fast check to rain threats, you have a potent sweeper on its own (such as against opposing weatherless) as well as a way to break opposing weather.
I've used weather moves on Pokémon without a speed-boosting ability (like Rain Dance Tornadus), but they're nearly dead weight against the weather they use (lol Starmie outspeeds and OHKOs with Thunder), nor did they ever seem to help that much against other weather beyond breaking it after the inducer was dead, but that honestly didn't help much in my games.
I've used weather moves on Pokémon without a speed-boosting ability (like Rain Dance Tornadus), but they're nearly dead weight against the weather they use (lol Starmie outspeeds and OHKOs with Thunder), nor did they ever seem to help that much against other weather beyond breaking it after the inducer was dead, but that honestly didn't help much in my games.